<div class="checkbox-list">
    {volist name="group" id="vo"}
    <div class="checkbox-item">
        <input class="checkbox" name="group" value="{$vo.id}" type="checkbox" <?php if(in_array($vo['id'],$user_groups))echo 'checked="checked"'; ?>>
        <span style="margin-left: 15px;">{$vo.group_name}</span>
    </div>
    {/volist}
</div>